Maybe he has depression..

I don't know about the drug tests.

but if he is acting like a normal teen or not would give some clues
does he have friends that seem nice?
does he take care of his personal hygiene
does he have chores or do his own laundry
mean, angry, or laid back and not caring about anything...
no normal interaction with others..

can she see any changes in his eyes & does he act like a totally different kid at times?

some kids are late bloomers
Is he a very shy kid???